The present invention relates to a toner recycling unit for recycling residual developer particles which are removed from a photoconductive element of an electrographic copier or printer. More particularly, the present invention relates to an apparatus which returns residual developer particles which have been removed from a photoconductive element by a cleaning device to a container holding the developer material.
In the process of electrophotographic or xerographic printing, a photoconductive member is employed to record an image. The photoconductive member, which typically is in the form of a belt or a drum, is charged to a substantially uniform potential to sensitize its photosensitive surface. In the case of a copying machine, the charged portion of the photosensitive surface is exposed to a reflected light image of an original document to be reproduced. The light image is recorded as an electrostatic latent image on the photoconductive member corresponding to the informational areas contained on the original document.
In the case of a printer connected to a computer, a similar process is used to record information on the photoconductive member. The charged portion of the photoconductive surface is exposed to a light image, the shape of which is controlled by input signals from the computer. For example, a laser or an LED array receiving input signals from the computer functions as an optical print head and illuminates the photoconductive member with a light image of a particular shape. Here too, an electrostatic latent image corresponding to desired informational areas is recorded on the photoconductive member.
After recording the electrostatic latent image on the photoconductive member, the latent image is developed by bringing a developer material or toner into contact with it. The developer material comprises triboelectrically charged toner particles and may also include carrier particles. The charged toner particles are attracted to the electrostatic latent image and form a powder or developed image on the photoconductive member corresponding to the electrostatic latent image. The developed image is subsequently transferred to a sheet of recording medium, such as a sheet of paper. Thereafter, the developed image is permanently affixed to the sheet in image configuration by a variety of methods, such as by fusing.
The above-mentioned operations may be carried out by arranging a number of stations in sequence about the photoconductive member. Thus, the photoconductive member is usually surrounded in sequence by a charging station to charge the photoconductive member, an imaging station to form an electrostatic latent image on the photoconductive member, a developing station to develop the electrostatic latent image on the photoconductive member, and a transfer station to transfer the developed image from the photoconductive member to the sheet of recording medium. A discharging station and a cleaning station are also arranged about the photoconductive member to ready it for use again.
As used herein, the term "electrographic printing apparatus" and the like are intended to include both copying and printing machines. Such machines include a developer unit operative to deliver toner to the photoconductive member. Typically the toner is stored in a storage compartment where it is mixed with a suitable carrier. The carrier often comprises iron or other metal particles. When mixed with the carrier, the toner acquires a suitable electrostatic charge so that it may easily be transferred to the photoconductive element to develop the latent electrostatic image formed thereon.
Usually, a cleaning device is also installed in the electrographic printing apparatus in order to remove toner and other developer particles which remain on the surface of the drum or the belt after the transfer of the developed image to the sheet of recording medium. In some cases, the cleaning device is integrated into the developer unit which alternately functions in either a developing or a cleaning mode. A variety of devices and methods have been used to clean residual developer particles from the photoconductive belt or drum.
For instance, one such cleaning device which is well known in the art comprises a brush which is used to remove the developer particles. The brush has a length substantially equal to the width of the photoconductive element in order that the entire photoconductive element be swept clean. The cleaning brush is formed using a suitable material to attract the toner particles, and it is positioned to face the photoconductive element so that it may contact its surface in order to remove the residual developer material.
In another well-known method of cleaning the photoconductive element, a scraper blade is applied to the photoconductive element. The scraper blade, typically made from a hard rubber material, is held against the photoconductive element and scrapes it free of residual toner particles. The residual developer particles which have thus been removed from the photoconductive element are then transferred from the cleaning device and discarded.
Thus, in many prior art devices the residual developer particles are scraped off by a blade or the like and are then discharged and discarded to the outside.
A more economical measure is to reuse the residual developer particles which have been removed from the photoconductive element by the cleaning device. As previously related, these residual particles consist of the carrier, which often comprises iron or other metal particles, and toner which did not transfer to the sheet of recording medium.
Heretofore, a variety of devices and methods have been used to recycle these residual developer particles. However, these devices and methods are often complex in structure and fail to provide an even distribution of the recycled developer particles within the developer unit which stores the developer particles. An even distribution of the residual particles throughout the developer unit is important so that some areas of the developer unit aren't emptied of developer material before other areas. This would result in uneven printing.
Accordingly, it is an object of the present invention to provide an apparatus for recycling residual developer particles which have been removed from a photoconductive member to a developer unit.
It is a further object of the present invention to provide an apparatus which maximizes the reuse of residual developer particles and does not suffer from the deficiencies of prior art recycling devices.
In particular, it is an object of the present invention to provide a recycling apparatus which is simple and cheap to construct, and can be attached to a disposable photoconductive belt assembly.
It is yet another object of the present invention to provide a recycling apparatus which provides an even distribution of the residual developer particles within the storage compartment which stores the developer particles.